1. Field of the Invention
The present invention relates to an X-ray diffraction apparatus which irradiates a sample with an X-ray and performs frame photographing in each angle range, an X-ray diffraction measuring method, and a control program.
2. Description of the Related Art
In the frame photographing for X-ray single crystal structure analysis, it is necessary to set an X-ray exposure time for one frame. This exposure time needs to be adjusted by a user according to sample crystalline property, X-ray source strength, and detector sensitivity. Conventionally, a user set the exposure time with reference to a default exposure time set on software or according to his experience, and controlled an apparatus to measure a diffracted X-ray. If the exposure time is short, sufficient diffraction intensity is not obtained, and therefore the analysis result is degraded and the measurement is performed again in this case. On the other hand, if the exposure time is unnecessarily long, the time required for the measurement becomes long.
Further, in a CCD or an IP detector which is used in such diffracted X-ray measurement, it is necessary to control open and close of a shutter for the frame exposure, and shutter-less measurement which makes the shutter control unnecessary cannot be realized. FIG. 10 is a diagram showing a conventional measurement sequence for one frame. In the example shown in FIG. 10, shutter control, goniometer control, CCD detection, and CCD read-out are performed in the order from (1) to (8). Then, overhead times are generated before and after the frame photographing for the shutter open and close operation.
In a semiconductor pixel detector, however, since the read-out time is less than several milliseconds for each frame, it has become possible to carry out continuous scan measurement while keeping the shutter open and to obtain a frame in synchronization with a goniometer. For example, each of non-patent documents 1 to 3 describes a semiconductor pixel detector which can obtain diffraction data in a continuous mode without opening and closing the shutter for each frame. In this semiconductor pixel detector, when crystal rotation starts, electronic control of the detector is used as a shutter and an image is recorded continuously, and therefore synchronization of opening and closing in the mechanical shutter is not necessary. By using the semiconductor pixel detector in this manner, it becomes possible to perform the shutter-less measurement which makes the shutter control unnecessary.